A sol-gel method with the aid of structure-directing surfactant was successfully used to synthesize mesoporous-assembled SrTiO3 nanocrystal photocatalysts by using strontium nitrate (Sr(NO3)(2)) and tetraisopropyl orthotitanate (TIPT) as precursors. Anhydrous ethanol (EtOH), ethylene glycol (EG), or EtOH/EG was selected as a solvent, while laurylamine hydrochloride (LAHC), cetyltrimethylammonium bromide (CTAB), or cetyltrimethylammonium chloride (CFAC) was used as a structure-directing surfactant. The photodegradation of methyl orange by SrTiO3 Was found to be affected by the crystallinity, specific surface area, and pore characteristic. The mesoporous-assembled structure with a high pore uniformity of SrTiO3 plays the most important role affecting the photocatalytic activity of the SMO3 photocatalyst. The SMO3 with the mesoporous-assembled structure and narrow pore size distribution synthesized at a calcination temperature of 700 degrees C, a heating rate of 1 degrees C min(-1), a LAHC-to-TIPT molar ratio of 0.25:1, and using an EtOH solvent provided the highest photocatalytic degradation activity, which was much higher than that of the non-mesoporous-structured commercial SMO3, (c) 2008 Elsevier B.V. All rights reserved.